WSSV susceptibility in the early life stages of Penaeus vannamei shows relationship with bodyweight.

White Spot Syndrome Virus (WSSV) continues to cause considerable loss to shrimp farmers globally with frequent outbreaks even in specific pathogen free Peneaus vannamei. Our studies showed that the bodyweight (BW) of PL has a bearing on their susceptibility to the virus. To test this hypothesis, PL of the same age group and family were grouped according to BW (10-20, 30-40, and 50-60 mg) and challenged through immersion route with two viral doses (10 and 10 virus copies/L of water). It was observed that the PL became susceptible to WSSV at ≥50 mg BW. In the 50-60 mg PL group, the higher challenge dose shows a sharp mortality curve with 100% mortality at 10 days post immersion, while the lower dose shows a steady increase in cumulative mortality that reaches 100% on the 13th day post immersion. The study also brings out that an in vivo viral load of approximately 3.5 to 4.5 × 10WSSV copies/100 ng shrimp DNA results in mortality. This is the first report on the relationship between BW and WSSV susceptibility in shrimp PL. Also reported here is a quantitative assessment of WSSV infection in P. vannamei PL and an optimized challenge protocol.